Touchscreen, as an input medium, is one of most simple, convenient and intuitive human-computer interaction manner for now. Integrating a touch feature into a display device has become a focus of display development for more and more panel display manufacturers.
FIG. 1A is a structural diagram of a typical mutual capacitance touch display panel in the prior art. As shown in FIG. 1A, a touch display panel 10A includes a plurality of scan lines 122 extending in a direction X, a plurality of data lines 124 extending in a direction Y, a plurality of touch driving electrodes 101 in blocks arranged in an array along the directions X and Y, and a plurality of touch sensing electrodes 103 arranged along the direction X. The plurality of touch driving electrodes 101 and the plurality of touch sensing electrodes 103 are formed such that they are perpendicular to each other. The touch driving electrodes 101 are connected to a control unit 108 via touch driving electrode lines 107, and the touch sensing electrodes 103 are connected to the control unit 108 via touch sensing electrode lines 109. The control unit 108 transmits touch driving signals to the touch driving electrodes 101 via the touch driving electrode lines 107. When a finger touches the panel from outside, a capacitance at each intersection 102 between the touch driving electrodes 101 and the touch sensing electrodes 103 changes, and signals based on the changes of the capacitances on the touch sensing electrodes 103 are received via the touch sensing electrode lines 109, for determining the touch location. As shown in FIG. 1A, the touch driving electrodes 101 and the touch sensing electrodes 103 are disposed in the same layer, and in order to prevent short circuits from being formed due to overlapping of the touch driving electrodes 101 and the touch sensing electrodes 103, touch driving electrodes 101 in the same row are connected by metal bridges 105
FIG. 1B is a schematic diagram of a typical self-capacitance touch display panel in the prior art. As shown in FIG. 1B, a touch display panel 10B includes a plurality of scan lines 126 extending in a direction X, a plurality of data lines 128 extending in a direction Y, a plurality of touch electrodes 104 in blocks arranged in an array along the directions X and Y. Each of the touch electrodes 104 is connected to a control unit 110 via a touch electrode line 106. The operation of the self-capacitance touch display panel 10B differs from that of the mutual capacitance touch display panel 10A in that the touch electrodes 104 in blocks of the self-capacitance touch display panel 10B functions as both of the touch driving electrodes and the touch sensing electrodes, and the control unit 110 transmits touch driving signals to the touch electrodes 104 via the touch electrode lines 106. When a finger touches the panel from outside, capacitances of the touch electrodes 104 change. The changes of the capacitances are sensed by the touch electrodes 104 for determining the touch location. As shown in FIG. 1B, in order to avoid signal disturbance between the touch electrodes 104 and the touch electrode lines 106, the touch electrodes 104 and the touch electrode lines 106 are positioned at different film layers, and connected to each other through via holes 108.
As described above, neither of the mutual capacitance touch display panel design as shown in FIG. 1A and the self-capacitance touch display panel design as shown in FIG. 1B is integrated with a pressure touch feature. Pressure touch means that when a finger touches a touch panel from outside with a pressure, the touch panel can generate a sensing signal depending on the amplitude of the pressure, so as to perform a corresponding operation. Currently, there are mainly two forms of pressure touch for a display panel: one is resistive pressure touch and the other is capacitive pressure touch. Where, the resistive pressure touch draws attention in the industry due to its high sensitivity and low cost. For a resistive pressure touch, a strain gauge is provided in a display panel, and the strain gauge has a resistance value changing with the deformation of the strain gauge. The resistance value or a voltage value of the strain gauge is measured to measure the pressure from outside.
FIG. 1C is a schematic diagram of a resistive Wheatstone bridge for test pressing pressures. Four resistors R1, R2, R3, R4 are connected to form a quadrilateral ABCD, referred to as four arms of the bridge. The quadrilateral ABCD has a diagonal BD connected to a galvanometer G, and another diagonal AC connected to a power source E. When the power source E is turned on, currents flow through each branch of the bridge. When the four resistors R1, R2, R3, R4 have resistances satisfying R1/R4=R2/R3, the Wheatstone bridge is in balance, and the galvanometer G reads zero current. When the four resistors R1, R2, R3, R4 have resistances not satisfying the above condition, potentials between points B and D are not equal to each other, and the galvanometer G reads a current other than zero, and the ratio of the resistances of the four resistors R1, R2, R3, R4 can be calculated from the output of the galvanometer G.
Currently, for a resistive pressure touch display panel, a strain gauge is typically disposed under a backlight layer of the display panel or at the periphery frame of the display panel. When the strain gauge is disposed under the backlight layer of the display panel, the thickness of the entire display panel will be increased, which is not conducive to the thinning of the display panel. Moreover, since the strain gauge is disposed under the backlight layer, the sensitive for finger touch will be significantly reduced, resulting in reduced touch sensitivity. When the strain gauge is disposed at the periphery frame of the display panel, since the periphery frame of the display panel is generally attached by double-sided adhesive tapes, and gap inevitably exists between the tape and the display panel, deformation of the surface of the display panel caused by pressure will be significantly influenced by the gap, resulting in reduced accuracy in pressure touch.